A glass edge chamfering machine is operated in such a manner that a glass plate is mounted on a rotary table of the main body of the machine, the rotary table is slowly rotated, and a diamond abrasive grinding wheel revolving at a high speed is contacted to the out edge of the glass plate, thereby finishing the cut edges of the glass plate to a smooth form. However, if the revolution speed of the rotary table is too high, the wearing of the diamond abrasive grinding wheel is too severe, as well as possibly breaking the glass plate, while, if the revolution speed of the rotary table is too low, the productivity drops.
Therefore, in the conventional device, as shown in FIGS. 1 and 2, a securing shaft 3a is installed on the top of a vertical pole 3 which is mounted to a main body 1, while a sector gear 20 is installed to the securing shaft 3a. Further a fixed plate 19 is attached above a first joint beam 4 which is connected through a rotary cylinder 18 to the sector gear 20, while the sector gear 20 is let to be meshed with a pinion gear 21 on which a second speed adjusting device 22 is installed.
This second speed adjusting device 22 and a first speed adjusting device 17 which is installed at a side of the joint beam 4 are connected to a reduction motor which is installed within the main body 1 and which is for rotating the rotary table 2. In this way, the volume of the first speed adjusting device 17 is adjusted so as for it to be fit to the chamfering angle and the chamfering width. Further, the revolution speed of the rotary table 2 is secondarily adjusted by utilizing the angle variation of the first joint beam 4 and the vertical pole 3 which can be adjusted in accordance with the size of the glass plate.
However, such a chamfering machine is suitable only for circular glass plates, because the revolution speed of the rotary table 2 is adjusted in accordance with the chamfering angle, the chamfering width and the size of the glass plates, to be chamfered. Accordingly, this chamfering machine is not suitable for glass plates having an elliptical or rectangular contour or other irregular contours which show irregular distances between the centre of the glass plate and its peripheral edges.
That is, as shown in FIG. 3, it is assumed that there are a circular glass plate 23 having a diameter of 1,000 mm, a rectangular glass plate 24 having edge lengths of 500 mm and 1,000 mm, and an elliptical glass plate 25 having cross lengths of 500 mm and 1,000 mm. All these glass plates are mounted on the rotary table 2, and imaginary divisions are made at angular intervals of degrees from the centre. Then it can be observed as follows.
That is, the circular glass plate 23 shows uniform intervals at its peripheries, and therefore, the speed adjustment is possible only by means of the first and second speed adjusting devices 17,22. However, in the case of the elliptical glass plate 25, the interval shows the minimum length at the point A, and, as advancing in the clockwise direction, the intervals a-j are gradually extended, until the interval becomes the maximum at the point B. After passing the point B, the intervals are gradually shortened, while, after passing the point C, the intervals are again gradually expanded, until it reaches the point D where the maximum interval is seen. Again, after passing the point D, the intervals are gradually shortened, until it reaches the point E where the minimum interval is encountered.
Accordingly, when an elliptical or rectangular glass plate 24 or 25 is chamfered, the processing advancing distance per unit of time becomes variable, and therefore, the finishing becomes crude, and the chamfering width becomes non-uniform. In a severe case, the diamond abrasive grinding wheel is worn out very easily, or the glass plate is broken.